The disclosed embodiments generally relate to laser optical ranging, and in particular, to using a coherent optical communication link for laser optical ranging and range rate measurements.
Ranging and range rate measurements are important parameters in spacecraft navigation and tracking. Because of the distances between space craft, between a terrestrial body and a spacecraft, or between terrestrial bodies, for example, Earth and Mars, accurate range and range rate measurements are difficult to achieve. Traditionally, these measurements are accomplished by measuring a Doppler shift of a microwave carrier that provides a target velocity along a line of sight. An exemplary Doppler tracking system may utilize a two-way X band (7.2-8.4 GHz) radio link to achieve average measurement accuracy ranges from 100 to 20 um/s at a 60 s integration time. Such RF based systems are subject to interference from various types of noise, in particular, the solar wind and plasma scintillation noise.
It would be advantageous to improve provide a system that provides communication at a high data rate, accurate pointing capability, and more precise ranging and range rate measurements with lower interference, while adding minimal cost over existing optical communication systems.